Add the fish pieces to a mixing bowl. Pour lemon juice all over and sprinkle salt, turmeric and red chilli powder. Set this aside for minimum 15 mins.
Powder together fennel seeds and pepper corn in a small grinder.
Heat a wide pan with ghee or oil.
Once it becomes hot, reduce the heat and add ginger garlic paste, green chilies. Fry until it turns aromatic, for about 60 seconds. Do not burn this.
Spread the oil well in the pan. Place the fish pieces. Fry them for 2 to 3 mins.
Turn them to the other side and fry again for another 2 to 3 mins.
Sprinkle half of the pepper and saunf powder evenly. Add curry leaves.
Turn them and sprinkle the rest of the powder. Fry until the fish is cooked through. To test, prick it with a fork at the thickest part, it should flake easily. The internal temperature should reach 145F or 65C.
Taste test and add more salt if required. If using garam masala powder you can sprinkle now. If you want more lemony flavor, add more lemon juice while serving.
Lemon pepper fish is ready to serve with roasted veggies or rice, rasam or as appetizer with soup.